Thermal sensitive element



1, 1957 N. T. TERP THERMAL SENSITIVE ELEMENT Filed March 4, 1964 vFi .1

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BY I

- A ORNE YS United States Patent 3,333,471 THERMAL SENSITIVE ELEMENT Norman T. Terp, Birmingham, Mich., assignor, by mesne assignments, to Antioch College, Yellow Springs, Ohio, a corporation of Ohio Filed Mar. 4, 1964, Ser. No. 349,262 4 Claims. (Cl. 73368.3)

The present invention relates to a temperature responsive force transmitting device of the type having a diaphragm or piston boot which is seated within the casing thereof and more particularly relates to a novel and improved means for maintaining a positive fluid type seal between the casing and the boot.

Temperature responsive force transmitting devices of this general type customarily have a diaphragm or piston boot which has a peripheral lip or bead sandwiched between the upper aud lower halves of the casing. Some difliculty has been experienced, however, in that the piston boot is subjected to considerable strains in use and the peripheral lip or bead tends to pull out of its original position. In doing so the casing to boot seal may be rendered imperfect and the life of the unit thereby shortened. Still further, in those devices which employ a boot of the type that fits over the inner end of the element piston, it has been found important to provide a means for preventing the boot from pulling away from the casing walls as the piston moves relative to the casing.

It is a principal and important object of the instant invention to obviate some of these and other disadvantageous characteristics of prior types of temperature responsive force transmitting devices.

More specifically, it is an object of the present inveution to groove portions of the boot engaging casing walls and to put portions of the boot under compression to force portions thereof into the grooves to provide a better casing to boot grip so as to prevent relative movement between portions of the boot and the casing walls in those areas where such movement retardation is desired.

These and other objects, advantages and features of the present invention will become apparent from time to time as the following specification proceeds and with reference to the accompanying drawings, wherein:

FIGURE 1 is a vertical sectional view through a temperature responsive force transmitting device constructed in accordance with the principles of the present invention and showing a portion of the element piston in side elevation; and

FIGURE 2 is an exploded view of the device illustrated in FIGURE 1.

The temperature responsive force transmitting device illustrated in the drawing comprises a base cup 11, a piston guide cup 12, a piston 13 guided for movement within the guide 12, and a boot 14 which is positioned Within the casing defined by the cup 11 and guide 12. The cup 11 is filled with a thermally expansible wax 15 and is itself formed of a thermally conductive material. As is well known in the art, rises in temperature ambient the cup 11 will cause the Wax 15 to expand and such wax expansion will act through the boot 14 to force the piston 13 to move extensibly from the guide 12. Upon cooling of the wax 15 the piston 13 can be returned to the position shown in FIGURE 1.

As is best viewed in FIGURE 2, the base cup 11 has an outturned annular flange 16 formed about the open end thereof. An annular wall 17 extends upwardly from the periphery of the flange 16 and terminates in an inwardly chamfered lip 18. In assembly, the wax 15 is preferably in the form of a pellet having an external surface conforming to the inner wall of the cup 11 and having a depression 19 formed therein which conforms generally to the shape of the base portion 20 of the boot 14.

Patented Aug. 1, 1967 A pair of spaced V-shaped concentric continuous grooves 21 are formed in the upper surface of the flange 16 and constitute an important feature of the instant invention.

As has previously been noted, the base portion 20 of the boot 14 preferably conforms to the depression 19 formed in the solid wax pellet 15. At any rate, the base portion 20 of the boot 14 depends from an outwardly extending resilient annular lip or bead 22 which bead is designed to seat upon the upper surface of the flange 16. It will be observed that the base portion 20 of the boot 14 tapers to a rounded end 23 from the head 22 and this rounded end is spaced from the inner side wall 24 of the base cup 11 and from the bottom 25 of the cup so that expansion of the wax 15 surrounding the base portion 20 will force the same upwardly and will thereby force the piston 13 to move extensibly from the guide 12.

It will be observed that in the unstressed condition shown in FIGURE 2, the diameter of the annular bead 22 is great enough so that the bead extendsover the outermost groove 21 but terminates short of the upstanding annular wall 17.

The piston guide cup 12 has an outturned annular flange 25 which has a diameter equal to the inner diameter of the upstanding annular Wall 17 so that the periphery thereof fits snugly within the annular wall 17 and this flange also has a pair of spaced V-shaped concentric continuous grooves 26 formed on the under surface thereof. A Well 27 is formed within the guide 12 and converges along a tapered" section 28 to a cylindrical section 29 which is adjacent and coaxial with a bore 30. The cylindrically shaped piston 13 is guided for movement within the bore 30 and has a conical inner end 31 which fits within a Well 33 of the boot 14 having a V-shaped inner end 33.

A pair of spaced V-shaped concentric and continuous grooves 34 are formed within the cylindrical section 29 of the well 27 to provide a positive fluid tight seal between the boot 14 and the casing.

A rim 35 depends from the periphery of the annular flange 25 a distance which is somewhat less than the thickness of the head 22 when that bead is in an unstressed condition. The thickness of the rim 35 is also somewhat less than the distance between the outermost groove 21 and the upstanding annular wall 17. The inner diameter of the rim 35 is, in fact, approximately equal to the outer diameter of the annular head 22.

As a consequence, when the base cup 11 and the guide cup 12 are placed in assembled relation the rim 35 is seated on the flange 16 so that the amount of compression of the head 22 is exactly determined and such squeezing of the bead 22 acts through the relatively incompressible rubber boot 14 to force parts of the neck portion 36 of the boot into the grooves 34 as portions of the bead 22 are likewise forced into the grooves 21. To this end, the outer diameter of the neck portion 36 is somewhat greater than the inner diameter of the cylindrical section 29. The resilient bead 22 and the neck portion 36 may be said to be non-conforming to the cooperable surfaces of the casing. By non-conforming it is meant that the bead and neck do not take on the general shape of the grooved associated casing surfaces when in an unstressed condition. When placed under suitable pressure, however, the non-conforming surfaces become conforming, as the boot material is resiliently forced into the grooves. It will be understood that all beads of this character will to some degree deform or become more conforming to the abutting surfaces. But, here, nonconforming refers to a difference in the general character of the material configuration.

It will also be noted that the grooves 21 and 26 are non-aligned when the flanges are secured together as shown in FIGURE 1. This nonalignment allows the bead material to be more tightly forced into the grooves. If the grooves were aligned, for instance, voids would exist on both sides of the bead at the same radial point and at that point, there would be no abutting flange to resiliently force the boot material into the grooves.

The base cup 11 and guide cup 12- are maintained in this assembled relation by peening or spinning the annular wall 17 over the flange 25 in the manner shown in FIG- URE 1.

It will be understood that this embodiment of the instant invention has been used for illustrative purposes only and that various modifications and variations in the invention may be effected without departing from the spirit and scope of the novel concepts thereof.

I claim as my invention:

1. A temperature responsive force transmitting device comprising:

a cup containing a thermally expansible material and having an out-turned flange,

a piston guide having an out-turned flange,

one annular groove formed within each flange,

a resilient boot having an integral annular bead formed therearound and having a nonconforming surface overlying said annular groove,

means interconnecting said flanges and compressing said bead therebetween and causing the bead material to be resiliently forced into and conforming to the groove.

said groove in the cup flange and the groove in the guide flange being circumferentially non-aligned,

a piston guided for rectilinear movement within said guide and seated on the boot,

whereby expansion of the thermally expansible material will cause said piston to move extensively from said guide and wherein the resilient forcing of the bead material into the groove seals the flanges and resists radial inward forces exerted on the bead.

2. A temperature responsive force transmitting device in accordance with claim 1 wherein at least two grooves are formed in each of said flanges and wherein the grooves in the cup and the grooves in the guide are circumferentially non-aligned.

3. A temperature responsive force transmitting device comprising:

a cup containing a thermally expansible material and having an out-turned flange,

a resilient boot having an integral annular bead formed therearound and lying on said flange and having a base portion extending within said cup and a neck portion extending in an opposite direction from the said bead,

a piston guide having an out-turned flange seated on said bead and having a well fitting snugly around said neck portion of said boot,

a piston guided for rectilinear movement in said guide and extending through said neck portion of said boot seated on the said base portion thereof,

a continuous groove formed about the inner wall of' said guide within the said well,

said neck portion having an initially non-conforming surface overlying said groove,

means interconnecting said flanges with one another and placing said neck portion of said boot and said bead under compression and resiliently forcing portions of said boot into said groove and causing said neck portion to conform to said groove.

4. A temperature responsive force transmitting device comprising? a base cup formed of a heat exchange material and containing a thermally expansible material and having an out-turned annular flange,

a resilient boot having an integral annular bead formed therearound and lying on said flange and having a from,

a piston guide cup having a well fitting snugly around 7 the said neck portion of said boot and having an outturned flange seated on said bead,

a rim formed about the periphery of one of said flanges and extending therefrom a distance less than the thickness of said bead in its unstressed condition,

a piston guided for rectilinear movement within said guide and seated on said base portion of said boot,

whereby expansion of the said thermally expansible material will cause said piston to move extensibly from said guide,

a plurality of continuous spaced grooves formed along the inner wall of said guide cup within said well and within the bead engaging faces of each of said flanges,

said bead and said neck portion being initially nonconforming to said grooves,

an annular wall extending outwardly from one of said flanges around the other of said flanges and crimped over the other of said flanges and maintaining said rim in engagement with the first mentioned flange and resiliently forcing said head and said neck portion of said boot into the said grooves, and causing said non-conforming surfaces. to conform to said grooves.

DAVID SCHONBERG, Primary Examiner.

LOUIS R. PRINCE, Examiner.

6O WILLIAM A. HENRY, J. RENJILIAN,

Assistant Examiners.

. base portion depending therefrom within said base a cup and a neck portion extending upwardly there-' 

1. A TEMPERATURE RESPONSIVE FORCE TRANSMITTING DEVICE COMPRISING: A CUP CONTAINING A THERMALLY EXPANSIBLE MATERIAL AND HAVING AN OUT-TURNED FLANGE, A PISTON GUIDE HAVING AN OUT-TURNED FLANGE, ONE ANNULAR GROOVE FORMED WITHIN EACH FLANGE, A RESILIENT BOOT HAVING AN INTEGRAL ANNULAR BEAD FORMED THEREAROUND AND HAVING A NONCONFORMING SURFACE OVERLYING SAID ANNULAR GROOVE, MEANS INTERCONNECTING SAID FLANGES AND COMPRESSING SAID BEAD THEREBETWEEN AND CAUSING THE BEAD MATERIAL TO BE RESILIENTLY FORCED INTO AND CONFORMING TO THE GROOVE. SAID GROOVE IN THE CUP FLANGE AND THE GROOVE IN THE GUIDE FLANGE BEING CIRCUMFERENTIALLY NON-ALIGNED, A PISTON GUIDED FOR RECTILINEAR MOVEMENT WITHIN SAID GUIDE AND SEATED ON THE BOOT, WHEREBY EXPANSION OF THE THERMALLY EXPANSIBLE MATERIAL WILL CAUSE SAID PISTON TO MOVE EXTENSIVELY FROM SAID GUIDE AND WHEREIN THE RESILIENT FORCING OF THE BEAD MATERIAL INTO THE GROOVE SEALS THE FLANGES AND RESISTS RADIAL INWARD FORCES EXERTED ON THE BEAD. 